[LTP] [PATCH v2] move_pages12: Make sure hugepages are available

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
> I'm sporadically running into SIGBUS in this testcase, not sure if it's 
> because of low memory or something else. Do you see it too?

None so far, but I haven't been running the test on anything else than
machines with just two numa nodes so far.

> I wonder if we should replace memset with MAP_POPULATE.

Isn't MAP_POPULATE best effort only?

I guess that we can then call mincore() to check if MAP_POPULATE really
populated the pages and possibly try dropping system caches and retry
again then produce TCONF if we happen to fail again.

> (gdb) bt
> #0  0x00003fffb16ac620 in .__memset_power8 () from /lib64/libc.so.6
> #1  0x0000000010003344 in memset (__len=67108864, __ch=0, __dest=0x3efffc000000) at /usr/include/bits/string3.h:84
> #2  alloc_free_huge_on_node (node=<optimized out>, size=67108864) at move_pages12.c:170
> #3  0x0000000010003648 in setup () at move_pages12.c:235
> #4  0x0000000010006ad4 in do_test_setup () at tst_test.c:705
> #5  testrun () at tst_test.c:778
> #6  tst_run_tcases (argc=<optimized out>, argv=0x3fffd1c7e488, self=<optimized out>) at tst_test.c:884
> #7  0x0000000010002f58 in main (argc=<optimized out>, argv=<optimized out>) at ../../../../include/tst_test.h:189
> 
> [pid 48425] 08:45:57.151242 write(2, "move_pages12.c:143: \33[1;34mINFO:"..., 82move_pages12.c:143: INFO: Allocating and freeing 4 hug
> epages on node 2
> ) = 82
> [pid 48425] 08:45:57.151287 mmap(NULL, 67108864, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_HUGETLB, -1, 0) = 0x3efffc000000
> [pid 48425] 08:45:57.151442 mbind(0x3efffc000000, 67108864, MPOL_BIND, [0x0000000000000004, 000000000000000000, 000000000000000000, 00
> 0000000000000000], 257, 0) = 0
> [pid 48425] 08:45:57.167377 munmap(0x3efffc000000, 67108864) = 0
> [pid 48425] 08:45:57.167486 write(2, "move_pages12.c:143: \33[1;34mINFO:"..., 82move_pages12.c:143: INFO: Allocating and freeing 4 hug
> epages on node 3
> ) = 82
> [pid 48425] 08:45:57.167554 mmap(NULL, 67108864, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_HUGETLB, -1, 0) = 0x3efffc000000
> [pid 48425] 08:45:57.167648 mbind(0x3efffc000000, 67108864, MPOL_BIND, [0x0000000000000008, 000000000000000000, 000000000000000000, 00
> 0000000000000000], 257, 0) = 0
> [pid 48425] 08:45:57.172293 --- SIGBUS {si_signo=SIGBUS, si_code=BUS_ADRERR, si_addr=0x3efffe000000} ---

Looks like we happen to got the signal when we try to fault third page,
at least if the si_addr is correct it points in the middle of the
mapping. So I guess that there is not enough continuous blocks to back
the mapping.

-- 
Cyril Hrubis
chrubis@suse.cz